As a structure of a resin-made pipe joint which is used for a tube for a fluid (for example, high purity liquid, ultrapure water, or chemical liquid) to be handled in a production process of various technical fields such as production of semiconductor devices, production of medical equipment and medicines, food processing, and chemical industry, for example, a structure of a resin-made pipe joint disclosed in Patent Literature 1 is known.
A structure of a resin-made pipe joint of this kind comprises a joint body, an inner ring (sleeve), and a press ring (fastening member). The joint body exhibits a cylindrical shape. The inner ring has a cylindrical press-inserting portion which can be press-inserted into the joint body, and a cylindrical coupling portion which can be press-inserted into a tube.
The press ring is configured so that the tube in a state where the coupling portion is press-inserted can be fixed to the joint body through the sleeve. Namely, the press ring is configured so that the state where the tube is connected to the joint body through the sleeve can be held.
In such a resin-made pipe joint, when the tube is connected to the joint body, a sealing portion which seals between the joint body and the press-inserting portion of the sleeve is formed. During a process of forming the sealing portion, in addition to the inner circumferential surface of the joint body, the outer circumferential surface of the press-inserting portion of the sleeve which is in close contact with the inner circumferential surface functions as an annular sealing surface.
The sleeve is produced by using a predetermined resin and molds. The molds comprise a gate port for pouring the resin (molten resin) which melts during production, into a cavity formed by the molds. In the molds, the gate port is placed in a portion where the outer circumferential surface (sealing surface) of the press-inserting portion of the produced sleeve is to be molded, and therefore a gate residue is generated on the sealing surface.
When the molten resin is poured into the cavity through the gate port, moreover, the molten resin flows so as to circumferentially spread in order to mold the sleeve, and then the sealing surface is formed. After the pouring of the molten resin is completed, therefore, a weld line is easily generated on the sealing surface.
In the case where a weld line or/and a gate residue is generated on the sealing surface, when the sleeve is used as it is, furthermore, the sealing property of the sealing portion is lowered. Therefore, there arises an inconvenience that a polishing step for removing a weld line or/and a gate residue must be disposed in a work of producing the sleeve.